“I cannot believe it. I’m shaking right now, maybe from the cold, or from the excitement, I don’t know,” he told reporters after finishing his third run in the men’s slopestyle snowboarding event on Sunday. “But I’m ecstatic.”

Appearing in his first Olympics, Gerard had a spotty performance in the first two of his three runs — falling in both — but under the rules of the event, one great run was all he needed. And that’s what he delivered in his final time on the snow, earning an 87.16 score, ahead of Canada’s Max Parrot and Mark McMorris.

“I can’t believe I got to land my run,” said Gerard, who came into the competition at the top of the world cup ranking. “Just to land a run would have been plenty for me and to get on the podium — but to get first is crazy.”

Now the youngest American man to medal at the Winter Olympics in nearly a century (since 1928), Gerard is also the youngest snowboarding gold medalist — period.

Slopestyle snowboarding was introduced at the Games in 2014, and an American has never not won gold there.

“After I landed the second jump I was like, ‘Come on, don’t blow it on the last one, let’s just make it through,’ ” Gerard said.

“The wind was really bad and the first two runs it was pretty tough,” he said, “but we got a nice little break on the third and I’m just happy I got to land.”